| 摘要: | 台灣是一個相對缺水的地區，尤其在夏季和秋季，由於降雨量較少，缺水問題更加嚴重。加上近年來氣候變遷導致氣候異常，台灣面臨著供需失衡、水資源分布不均和水資源管理挑戰等問題。
本研究使用美國地質調查所（USGS）發展的地下水流模擬程式MODFLOW，並透過地下水環境模擬軟體(GMS)來建立地下水流數值模式。探討農業用水對美濃、旗山地區地下水資源之影響。本研究模擬時間為2020及2021年，蒐集屏東平原水文及地文資料，包含土地利用、降雨、抽水、河川流量、水力傳導係數等資料來建立美濃、旗山地區地下水模式，模擬在有農業用水的情況下，地下水資源之變化，模式驗證結果顯示相關係數(R)除土庫為中度相關，但其值0.65接近高度相關，其餘皆大於0.7，為高度相關；均方根誤差(RMSE)則大約在1m左右，顯示模式能模擬實際情況。
研究結果顯示在沒有灌溉情況下，2020年，美濃、旗山灌區之補注量為16.94百萬立方公尺，里港灌區補注量為2.37百萬立方公尺；有灌溉情況下，美濃、旗山灌區之補注量為19.11百萬立方公尺，里港灌區補注量為3.6百萬立方公尺。2021年美濃、旗山灌區之補注量為13.87百萬立方公尺，里港灌區補注量為2.08百萬立方公尺；有灌溉情況下，美濃、旗山灌區之補注量為15.54百萬立方公尺，里港灌區補注量為3.26百萬立方公尺。
分析2020~2021年變化趨勢，美濃、旗山地區在有無灌溉下蓄水變化量皆為負值，判斷其原因為抽水導致；里港地區2020年在灌溉條件下，蓄水變化量有增加趨勢，但整體蓄水變化依然為負值。2021年加入灌溉水後，蓄水變化量來到正值，補注效果顯著。根據本研究結果可知，灌溉用水可以一定程度有效保存於地下。因此，合理的灌溉設計和管理對與保存水資源是一個重要的議題。
;Taiwan is a relatively water-deficient region, particularly during the summer and autumn seasons when rainfall is scarce, exacerbating the water shortage problem. In addition, recent years have seen abnormal weather patterns due to climate change, posing challenges such as supply-demand imbalances, uneven distribution of water resources, and water resource management issues for Taiwan.
This study utilizes the groundwater flow simulation program MODFLOW, developed by the United States Geological Survey (USGS), and employs the groundwater environment simulation software (GMS) to establish a numerical model for groundwater flow. The aim is to discuss the impact of agricultural water use on groundwater resources in the Meinong and Qishan areas. The simulation period for this study is 2020 and 2021. Hydrological and geographic data of the Pingtung Plain, including land use, rainfall, pumping, river flow, and hydraulic conductivity, are collected to establish groundwater models in the Meinong and Qishan areas, simulating existing agricultural water use and its effect on groundwater resources. The model verification results indicate that the correlation coefficient (R) is moderately correlated, except for the soil bank, with a value of 0.65, which is close to highly correlated. The remaining coefficients are greater than 0.7, indicating a high correlation. The root mean square error (RMSE) is approximately 1m.
The research findings demonstrate that, without irrigation, the recharge volume of the Meinong and Qishan irrigation districts in 2020 will be 16.94 million cubic meters, and the recharge volume of the Ligang irrigation district will be 2.37 million cubic meters. When considering irrigation, the recharge volume for the Meinong and Qishan irrigation districts is projected to be 19.11 million cubic meters, while the Ligang irrigation district is expected to have a recharge volume of 3.6 million cubic meters. In 2021, the recharge volume for the Meinong and Qishan irrigation districts will be 13.87 million cubic meters, with the Ligang irrigation district having a recharge volume of 2.08 million cubic meters. Considering irrigation, the recharge volume for the Meinong and Qishan irrigation districts is estimated to be 15.54 million cubic meters, while the Ligang irrigation district is anticipated to have a recharge volume of 3.26 million cubic meters.
Analysis of the trend from 2020 to 2021 reveals that the water storage changes in the Meinong and Qishan regions were negative regardless of irrigation, indicating that the decline was caused by water extraction. In the Ligang area, water storage changes showed an increasing trend in 2020 under irrigation conditions, yet the overall water storage change remained negative. However, in 2021, with the addition of irrigation water, the water storage change turned positive, demonstrating a significant replenishment effect. Based on the findings of this study, it can be concluded that irrigation can effectively contribute to underground water conservation to some extent. Therefore, proper irrigation design and management play a crucial role in water resource preservation. |
